Net Loss per Share - Schedule of Potentially Dilutive Securities not Included in Calculation of Dilutive Net Loss per Share (Detail) - shares		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities not included in calculation of dilutive net loss per share		32,164,398	29,562,081	33,901,534
Class B Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities not included in calculation of dilutive net loss per share	[1]	23,093,860	23,094,221	23,094,221
Common Stock Options Granted Under the Plan [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities not included in calculation of dilutive net loss per share		7,056,035	4,453,357	2,531,143
Restricted Stock Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities not included in calculation of dilutive net loss per share				11,667
Common Stock Options Granted Under the Letter Agreement [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities not included in calculation of dilutive net loss per share				6,250,000
Common Stock Warrants [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities not included in calculation of dilutive net loss per share		2,014,503	2,014,503	2,014,503

[1] Shares of Class B Common Stock do not share in the Company’s earnings and are not participating securities.  Accordingly, separate presentation of loss per share of Class B Common Stock under the two-class method has not been provided.  Each share of Class B Common Stock (together with a corresponding vTv Unit) is exchangeable for one share of Class A Common Stock.